As display technology develops quickly, a touch screen has already pervaded people's life gradually. At present, the existing capacitive in cell touch screen supports a multi-touch function, has a higher light transmittance and a lower total power consumption, and its contact surface has a high scale of hardness and service life is long.
For example, a projected capacitive touch mainly utilizes capacitive sensing formed due to a contact between transparent electrodes on the touch screen and fingers of humans or conductive objects, and converts into coordinate files available for a touch system to judge by controlling operations of an integrated circuit chip. In the configuration of the projected capacitive touch screen, the transparent electrodes, i.e., touch-driven electrodes and touch-sensed electrodes, are arranged in a manner of interleaved X and Y axes. These transparent electrodes are connected in the surrounding area of the touch screen through a sensing channel of a metal wire and a control chip. When no touch occurs, each of the transparent electrodes has a fixed capacitance value, i.e., a parasitic capacitance. When a touch occurs, there is a sense between the conductive objects and the transparent electrodes to form a coupling capacitance, and a sensing capacitance value measured by the control chip is no longer the original fixed capacitance value. Therefore, according to a change of the measured capacitance value, a coordinate position of a touch point can be calculated. A self-capacitive touch determines a position of the touch point by sensing a change of a capacitance value between each node and the ground, while a mutual-capacitive touch determines the position of the touch point by sensing a change of a capacitance value between X and Y axes of each node.
In general, the touch function of the capacitive in cell touch screen is implemented through a touch driving circuit in the touch screen. The known touch driving circuit outputs a touch driving signal to a touch driving electrode at each time. This touch driving signal controls the touch driving electrode to charge a capacitance of a corresponding node, and at the same time the touch sensing electrode senses a change of a capacitance value of the corresponding node, so as to determine the position of the touch point. However, as a touch display screen becomes popular, a problem of an excessive RC delay would occur in a large-size touch display screen at present, that is, when the touch driving circuit charges the node, a node capacitor C would increase continuously as the number of the touch points increases, and a resistance value R would increase continuously as a distance of the touch driving node increases. Therefore, in the process of touch driving of the touch screen, the corresponding RC delay would increase gradually, and when the increase of the RC delay exceeds one fifth of scanning time of the gate-integrated driving circuit, the problem that the touch points cannot be calculated correctly would occur.
Therefore, how to reduce the RC delay of touch driving of the touch screen and ensure the correct determination of the position of the touch points is a problem to be solved urgently by those skilled in the art.